Mr Palmer has written to Ms Credlin to say he regrets if he caused her any offence by claiming Mr Abbott's $5.5 billion paid parental leave scheme was designed so she would benefit if she fell pregnant.

Ms Credlin, who served as Mr Turnbull's deputy chief of staff when he was Liberal leader in 2009, has publicly spoken about her difficulties in trying to conceive through IVF.

This morning Macquarie Radio host Alan Jones demanded Mr Turnbull explain why he had not publicly leapt to her defence, especially given he had dinner with Mr Palmer last week.

"I was waiting, I couldn't hear any echo from Canberra of Malcolm publicly springing into defence and saying what reprehensible, disgraceful behaviour this is and what an obscenity this woman who worked for me should be attacked in such a way, I was trying to hear the echo from Canberra, Malcolm, I couldn't hear any reverberation at all," Jones said.

"I'll tell you what I did, Alan, because I don't want to create any more pain for Peta than she's already suffered," Mr Turnbull said.

"What I did was, and I told Peta about this at the time... I sent a message to Palmer telling him he should man up and apologise. I then rang him and spoke to him and told him in no uncertain terms that he should apologise.

"He sent the note, which obviously wasn't an adequate apology, and he has been rightly condemned for it," he added.

Jones then lashed out at Mr Turnbull for dining with Mr Palmer, who has ratcheted up his attack on the Liberal National Party, of which he was once a member and donor.

"Just imagine a senior member of the government, inviting to have dinner with him a bloke who is perhaps the most trenchant critic of that person's leader," Jones said.

"Did you raise all of these issues with Palmer at dinner, did you defend Tony Abbott to Palmer?"

"I defend Tony Abbott all the time, Tony and I are a team, the thing that has distressed me this week, people, yourself, Andrew Bolt in particular, have set out to suggest that there is dissension in the Government, that there are challenges to his leadership," Mr Turnbull said.

"I think it's just very sad that you and Bolt are doing the work of the Labor Party in undermining the Abbott Government."